The conventional technique for producing cast members such as manhole assemblies comprises the steps of pouring the cast material, i.e. concrete, into a mold containing a cylindrical shaped grid of wires placed within the mold and serving as a reinforcement for the cast member. The wire grid typically comprises a plurality of vertically aligned wires joined to horizontally aligned hoops, forming the grid-like framework. When the cast material is set, the cast member is removed from the mold. The wire reinforcement is embedded in the cast material, typically concrete.
Investigation and analysis by the authorities responsible for establishing specifications for manhole assemblies have recently developed new specifications, which permit the use of one or more lines of hoop steel in place of the grid-like wire mesh of conventional design. These new specifications result from the fact that once manhole assemblies are installed, they are in compression whereas reinforcement steel has been utilized in concrete to provide reinforcements for a cast member under tension.
Thus, the new specifications require that circular manholes need only be provided with steel reinforcement satisfactory for handling purposes preparatory to in-ground installation with the result that the new specifications permit manhole assemblies of certain sizes and thicknesses to have a reduction in reinforcement steel content enabling the use of round steel hoops in the place of conventional steel mesh (i.e. welded wire fabric arranged in a grid-like pattern). In view thereof, it is necessary to provide proper support, alignment and positioning of the steel hoops in place of the conventional longitudinal elements used in conventional designs and which are no longer required.